How disorder influences order and vice versa--mutual effects in fusion proteins containing an intrinsically disordered and a globular protein.

Intrinsically disordered proteins (IDPs) are functional proteins either fully or partly lacking stable secondary and tertiary structure under physiological conditions that are involved in important biological functions, such as regulation and signalling in eukaryotes, prokaryotes and viruses. The function of many IDPs relies upon interactions with partner proteins, often accompanied by conformational changes and disorder-to-order transitions in the unstructured partner. To investigate how disordered and ordered regions interact when fused to one to another within the same protein, we covalently linked the green fluorescent protein to three different, well characterized IDPs and analyzed the conformational properties of the fusion proteins using various biochemical and biophysical approaches. We observed that the overall structure, compactness and stability of the chimeric proteins all differ from what could have been anticipated from the structural features of their isolated components and that they vary as a function of the fused IDP.

Protein flexibility in psychrophilic and mesophilic trypsins. Evidence of evolutionary conservation of protein dynamics in trypsin-like serine-proteases.

To shed light on the molecular features related to cold-adaptation in serine-proteases, we have carried out molecular dynamics simulations of homologous mesophilic and psychrophilic trypsins, with particular attention to evaluation of intramolecular interactions and flexibility. Psychrophilic trypsins present fewer interdomain interactions and enhanced localized flexibility in regions close to the catalytic site. Notably, these regions fit well with the pattern of protein flexibility previously reported for psychrophilic elastases. Our results indicate that specific sites within the serine-protease fold can be considered hot spots of cold-adaptation and that psychrophilic trypsins and elastases have independently discovered similar molecular strategies to optimize flexibility at low temperatures.